Sublingual application of allergen extracts in specific immunotherapy is a modern approach aimed at improving patient treatment acceptance through reduced serious side effects. This therapeutic approach has proven to be efficacious and safe for the treatment of allergies caused by airborne allergens: 1) studies have shown a rapid onset of action, as early as seven days after beginning treatment; 2) a strong effect during treatment, superior to most forms of symptomatic treatment; 3) a lasting effect after cessation; 4) a preventive effect against new sensitizations and new-onset asthma; and 5) an unprecedented safety profile compared to the subcutaneous route. SLIT is an established treatment option for moderate to severe allergic rhinoconjunctivitis with or without asthma, which can be given to adults as well as to children above five. The complexity of the treatment of this condition mandates expert care by an experienced allergologist.